1 files changed, 18 insertions, 20 deletions
diff --git a/MdePkg/Library/UefiMemoryLib/ScanMem64Wrapper.c b/MdePkg/Library/UefiMemoryLib/ScanMem64Wrapper.c
index c5f0762ebe..228c864b04 100644
--- a/MdePkg/Library/UefiMemoryLib/ScanMem64Wrapper.c
+++ b/MdePkg/Library/UefiMemoryLib/ScanMem64Wrapper.c
@@ -26,25 +26,22 @@
 #include "MemLibInternals.h"
 
 /**
-  Scans a target buffer for a 64-bit value, and returns a pointer to the
-  matching 64-bit value in the target buffer.
+  Scans a target buffer for a 64-bit value, and returns a pointer to the matching 64-bit value
+  in the target buffer.
 
-  This function searches target the buffer specified by Buffer and Length from
-  the lowest address to the highest address at 64-bit increments for a 64-bit
-  value that matches Value. If a match is found, then a pointer to the matching
-  value in the target buffer is returned. If no match is found, then NULL is
-  returned. If Length is 0, then NULL is returned.
-
-  If Buffer is NULL, then ASSERT().
+  This function searches target the buffer specified by Buffer and Length from the lowest
+  address to the highest address for a 64-bit value that matches Value.  If a match is found,
+  then a pointer to the matching byte in the target buffer is returned.  If no match is found,
+  then NULL is returned.  If Length is 0, then NULL is returned.
+  If Length > 0 and Buffer is NULL, then ASSERT().
   If Buffer is not aligned on a 64-bit boundary, then ASSERT().
-  If Length is greater than (MAX_ADDRESS - Buffer + 1), then ASSERT().
+  If Length is greater than (MAX_ADDRESS – Buffer + 1), then ASSERT(). 
 
-  @param  Buffer  Pointer to the target buffer to scan.
-  @param  Length  Number of bytes in Buffer to scan.
-  @param  Value   Value to search for in the target buffer.
+  @param  Buffer      Pointer to the target buffer to scan.
+  @param  Length      Number of bytes in Buffer to scan.
+  @param  Value       Value to search for in the target buffer.
 
-  @return Pointer to the first occurrence or NULL if not found.
-  @retval NULL  if Length == 0 or Value was not found.
+  @return A pointer to the matching byte in the target buffer or NULL otherwise.
 
 **/
 VOID *
@@ -55,12 +52,13 @@ ScanMem64 (
   IN      UINT64                    Value
   )
 {
+  if (Length == 0) {
+    return NULL;
+  }
+
   ASSERT (Buffer != NULL);
   ASSERT (((UINTN)Buffer & (sizeof (Value) - 1)) == 0);
-  ASSERT (Length <= MAX_ADDRESS + (UINTN)Buffer + 1);
+  ASSERT ((Length - 1) <= (MAX_ADDRESS - (UINTN)Buffer));
 
-  if ((Length /= sizeof (Value)) == 0) {
-    return NULL;
-  }
-  return (VOID*)InternalMemScanMem64 (Buffer, Length, Value);
+  return (VOID*)InternalMemScanMem64 (Buffer, Length / sizeof (Value), Value);
 }